1. Field of the Invention
The present invention relates to an X-ray image reader for reading an X-ray image stored in an X-ray image-storing member having an X-ray storing surface formed of, for example, a storage fluorescent member.
2. Description of the Related Art
The X-ray image-storing member formed by a storage fluorescent member has been known. In a case where an X-ray measurement is performed by using such X-ray image-storing member in order to investigate a crystal structure of a specimen, the specimen is irradiated with X-ray and the X-ray image-storing member is exposed by X-ray emitted from the specimen, for example, diffracted X-ray or scattered X-ray. Therefore, a latent image of energy is formed in an X-ray receiving surface of the X-ray image storing member at a coordinates position, which corresponds to a diffraction angle of the diffracted X-ray or the scattered X-ray thus generated.
The storage fluorescent member has the nature of holding a latent image of energy at a position thereof to which X-ray impinges and the nature of converting the latent image of energy into light when a portion thereof which holds the latent image is irradiated with emission stimulating light, such as laser light. Therefore, it is possible to know intensity of X-ray contributed to the formation of the latent image by detecting externally emitted light from the storage fluorescent member when the storage fluorescent member holding the latent image of energy is irradiated by laser light. Further, it is possible to know the diffraction angle of X-ray contributed to the formation of latent image by the coordinates of the storage fluorescent member from which light is emitted.
As an X-ray image reader utilizing the principle mentioned above, the present inventors had proposed a double-head type X-ray image reader 100, which is shown in FIG. 10. In the X-ray image reader 100, a first read head 101a and a second read head 101b are arranged symmetrically about a center axis X0 and laser light from an emitting optical system 102 including a laser light source is divided so that laser light portions are emitted externally through the first and second read heads 101a and 101b, respectively.
Each of the first read head 101a and the second read head 101b can take externally supplied light therein. The light thus taken into the read head is guided to a receiving optical system 103 including a photoelectric converter and then converted into an electric signal by the photoelectric converter.
In order to read an X-ray latent image stored in an X-ray image storing member 104 by using the X-ray image reader 100, the X-ray image storing member 104 takes in the form of a concaved and semi-cylindrical configuration and the center axis X0, which is a rotation center of the first and second read heads 101a and 101b is positioned at substantially a center of the semi-cylindrical X-ray image storing member 104. The first and second read heads 101a and 101b are rotated about the axis line X0 in a direction shown by an arrow A, while the whole X-ray image reader 100 is moved in parallel to the axis line X0 in a direction shown by an arrow B.
With the rotation of the first and second read heads 101a and 101b in the arrow direction A and the straight vertical movement of the whole X-ray image reader in the arrow direction B, the first and second read heads 101a and 101b are alternatively moved to a position opposing to the X-ray image storing member 104, so that a wide area of the X-ray image storing member 104 is scanned by these read heads. In this scanning, laser light from the first read head 101a or the second read head 101b scans a surface of the X-ray image storing member 104 and, when the laser light scans a portion of the surface in which a latent image of energy is formed, fluorescent light is emitted from that portion.
This light is taken in the receiving optical system 103 through the first read head 101a or the second read head 101b and converted into an electric signal, on the basis of a level of which intensity of the light can be obtained. Since the intensity of light corresponds to intensity of X-ray contributed to a formation of the latent image of energy, it is possible to know the intensity of X-ray by measuring the intensity of light.
The conventional double-head type X-ray image reader 100 constructed as mentioned above makes it possible to perform a high speed reading since two read heads 101a and 101b are used alternatively and effectively. However, this double-head type X-ray image reader 100 requires a processing technique for matching the two data obtained alternatively by the read heads 101a and 101b with one reference level. Despite use of such technique a complete processing may not be achieved. Therefore, the conventional double-head type X-ray image reader may not perform a highly precise measurement.
Assuming that there is a difference in output between the first and second read heads 101a and 101b, a correction for compensating for the difference, that is, an intensity correction is required. Further, when the first read head 101a and the second read head 101b are arranged oppositely with an angular interval, which is not exactly 180 degrees, a compensation for the angle error, that is, the angle error correction is necessary.
In general, such corrections are performed by preliminarily reading a reference object by the two read heads, respectively, preliminarily detecting the difference or error from a result of the reading and electrically processing the difference or error thus obtained by using arithmetic operating means, such as a computer. However, it is very difficult to completely connect the measuring results from the two read heads with using the same reference level. This difficulty is not limited to the double-head type X-ray image reader and the same difficulty also exists in a multi-head type X-ray image reader having three or more read heads.
The present invention was made in view of the above-mentioned problem and an object of the present invention is to provide an X-ray image reader for reading an X-ray image by using a plurality of read heads, which is capable of performing a precise reading.
The object above-mentioned is achieved by the present invention, which is as follows:
(1) An X-ray image reader according to a first aspect of the present invention is featured by comprising a plurality of read heads, scan drive means for scanning an X-ray image storing member by moving the read heads, first control means for performing a process for reading an X-ray image held on the X-ray image storing member by using at least two of the read heads and second control means for performing a process for reading the X-ray image held on the X-ray image storing member by using any one of the read heads.
According to the X-ray image reader of the first aspect of the present invention, it is possible to perform a measurement with using a plurality of read heads, that is, a multi-head mode measurement, by the first control means. Alternatively, it is possible to perform a measurement with using one read head, that is, a single head mode measurement, by the second control means. Therefore, the multi-head mode measurement may be alternatively performed when it is necessary to obtain a result of measurement at high speed regardless of preciseness thereof, that is, when a high-speed measurement is to be performed. On the other hand, the single head mode measurement may be alternatively performed when a precise measurement is to be performed even if the measuring speed is low to some extent.
The single head mode measurement makes it possible to perform a highly precise measurement since there is no situation in which measuring error occurs between the read heads. That is, X-ray image reader according to the present invention makes it possible to perform the highly precise image reading in spite of having the structure for the multi-head mode function.
(2) The scan drive means of the X-ray image reader may drive the read heads to alternatively face them to the X-ray image storing member such that the read heads scan the X-ray image storing member alternatively. In such case, it is possible to perform the high-speed measurement though preciseness of measurement is somewhat degraded.
(3) The scan drive means may include rotary drive means for rotating the read heads and straight drive means for driving the read heads in a direction perpendicular to a plane in which the read heads rotate. In such case, the read heads may be arranged in different angular positions with respect to the rotating direction of the read heads.
According to the X-ray image reader constructed as mentioned above, it is possible to perform a main scan for the X-ray image-storing member in lateral direction by rotating the read heads and, further, to perform a sub scan for the X-ray image storing member by moving the read heads straightly in vertical direction. By such main and sub scans for the X-ray image storing member, it is possible to scan a wide surface of the X-ray image storing member by alternately using the read heads.
(4) The X-ray image-storing member may have an X-ray storing surface formed of a storage fluorescent member. The X-ray image reader may further include a light emitting optical system for emitting emission stimulating light to the read heads and a light receiving optical system for receiving light emitted from the X-ray image storing member through the read heads. The second control means may select one of the read heads as a read head for emitting the emission stimulating light through the light emitting optical system and perform the read processing by use of the read head selected.
X-ray image reader as mentioned above may select the one read head to be used by supplying one of the read heads with emission-stimulating light such as laser light. The one read head thus selected may perform read processing.
Further, the xe2x80x9cstorage fluorescent memberxe2x80x9d is a radiation detector capable of storing energy and is also called emission fluorescent member, which is made by forming a film of emission fluorescent member, such as fine crystal of BaFBr:Er2+, on a surface of a flexible film, a flat film or other member. The storage fluorescent member has a nature of storing energy of X-ray, etc., and emitting the stored energy as light when it is irradiated with emission stimulating light such as laser light.
That is, when a portion of the storage fluorescent member is irradiated with X-ray, etc., energy thereof is stored in that portion of the storage fluorescent member as a latent image. When the storage fluorescent member is irradiated with emission stimulating light such as laser light, Energy of the latent image is discharged externally as light. It is possible to measure diffraction angle and intensity of X-ray contributed to the formation of the latent image by detecting the thus externally emitted light by means of a photo-tube, etc. Sensitivity of the storage fluorescent member is in the order of 10 to 60 times that of a conventional X-ray film and dynamic range thereof is as wide as 106 to 108.
(5) The second control means may select the one read head, which emits emission-stimulating light, by ON/OFF controlling of the emission stimulating light. With such construction, a mechanical structure of the X-ray image reader becomes simple since the read heads can be selected without necessity of providing a mechanical light shield means such as a beam stopper or a shutter.
(6) Alternatively, the second control means may select the one read head, which emits emission stimulating light, by arranging a beam stopper on an optical path of the light emitting optical system for one of the read heads, which is not used, and arranging no beam stopper on an optical path of the light emitting optical system for the read head, which is used. In this construction of the second control means, it is possible to select a read head without using any complicated electric control system.
(7) According to a second aspect of the present invention, an X-ray image reader comprises a pair of read heads separated from each other by an angle of 180 degrees, rotary drive means for rotating the read heads, straight drive means for moving the read heads in a straight direction perpendicularly to the plane on which the read heads rotate, first control means for reading an X-ray image stored in an X-ray image storing member by using both of the two read heads and second control means for reading the X-ray image stored in the X-ray image storing member by using any one of the two read heads.
The X-ray image reader using two read heads as mentioned above is one so-called double-head type X-ray image reader belonging to the multi-head type X-ray image reader using a plurality of read heads.
In the X-ray image reader according to the second aspect of the present invention, it is possible to perform a measurement with using the two read heads, that is, a double-head mode measurement, by the first control means. Alternatively, it is possible to perform a measurement with using one read head, that is, a single-head mode measurement, by the second control means. Therefore, it is possible to perform the double-head mode measurement when it is necessary to obtain a result of measurement at high speed regardless of preciseness thereof and to perform the single-head mode measurement when a precise measurement is to be performed.
In the single-head mode measurement, it is possible to perform a highly precise measurement since measuring error between the read heads does not occur. That is, the X-ray image reader constructed as mentioned above may perform the highly precise image reading in spite of the double-head mode X-ray image reader which is one kind of a multi-head mode X-ray image reader.
(8) In the X-ray image reader having the double-head mode as mentioned above, X-ray image storing member may have an X-ray imaging surface formed of a storage fluorescent member. The X-ray image reader may further include a light emitting optical system for supplying emission-stimulating light to the two read heads and a light receiving optical system for receiving light emitted from the X-ray image-storing member through the two read heads. The second control means may select one of the read heads as a read head for emitting the emission stimulating light through the light emitting optical system and perform the read processing by any one of the read heads.
In the above-mentioned X-ray image reader, the one read head to be used is selected depending on which read head is supplied with emission-stimulating light, such as laser light The one read head thus selected may perform reading processing.
(9) In the X-ray image reader having the double-head mode as mentioned above, the second control means may select the one read head, which emits emission stimulating light, by ON/OFF controlling the emission stimulating light. With such construction, a mechanical structure of the X-ray image reader becomes simple since the read heads can be selected without necessity of providing a mechanical light shield means such as a beam stopper or a shutter.
(10) Alternatively, in the X-ray image reader having the double-head mode as mentioned above, the second control means may select the one read head, which emits emission stimulating light, by arranging a beam stopper on an optical path of the light emitting optical system for one of the read heads, which is not used, and arranging no beam stopper on an optical path of the light emitting optical system for the read head, which is used. In this construction of the second control means, it is possible to select a read head without using any complicated electric control system.